Genetic variations at urotensin II and urotensin II receptor genes and risk of type 2 diabetes mellitus in Japanese

Urotensin II system in chronic kidney disease

Chronic kidney disease (CKD) is a progressive and long-term condition marked by a gradual decline in kidney function. CKD is prevalent among those with conditions such as diabetes mellitus, hypertension, and glomerulonephritis. Affecting over 10% of the global population, CKD stands as a significant cause of morbidity and mortality. Despite substantial advances in understanding CKD pathophysiology and management, there is still a need to explore novel mechanisms and potential therapeutic targets. Urotensin II (UII), a potent vasoactive peptide, has garnered attention for its possible role in the development and progression of CKD. The UII system consists of endogenous ligands UII and UII-related peptide (URP) and their receptor, UT. URP pathophysiology is understudied, but alterations in tissue expression levels of UII and UT and blood or urinary UII concentrations have been linked to cardiovascular and kidney dysfunctions, including systemic hypertension, chronic heart failure, glomerulonephritis, and diabetes. UII gene polymorphisms are associated with increased risk of diabetes. Pharmacological inhibition or genetic ablation of UT mitigated kidney and cardiovascular disease in rodents, making the UII system a potential target for slowing CKD progression. However, a deeper understanding of the UII system's cellular mechanisms in renal and extrarenal organs is essential for comprehending its role in CKD pathophysiology. This review explores the evolving connections between the UII system and CKD, addressing potential mechanisms, therapeutic implications, controversies, and unexplored concepts.

The Role of Urotensin-II in Obesity and Metabolic Syndrome in Pediatric Population

Background: Urotensin-II (U-II) is a short cyclic peptide that is widely recognized as one of the most potent vasoconstrictors. U-II plays a role in the pathophysiology of MS, participating in the development of essential hypertension, insulin resistance, hyperglycemia, and a proinflammatory state. Methods: This study comprised 52 obese children and adolescents with a body mass index (BMI) z score > 2, aged 10 to 18 years. Serum levels of U-II were assessed using an enzyme-linked immunosorbent assay along with other standard biochemical parameters. Results: Elevated serum levels of U-II were recorded in the group of obese subjects with MS when compared with the group of obese subjects without MS (4.99 (8.97–3.16) vs. 4.17 (5.17–2.03) ng/mL, median and IQR, p = 0.026). Furthermore, a subgroup of study subjects with high blood pressure had significantly higher U-II levels in comparison with the normotensive subgroup (4.98 (7.19–3.22) vs. 3.32 (5.06–1.97) ng/mL, p = 0.027), while the subgroup with a positive family history of high blood pressure had significantly higher U-II levels when compared with subjects who had a negative family history of elevated blood pressure (5.06 (6.83–4.45) vs. 3.32 (6.13–2.21) ng/mL, p = 0.039). Conclusions: To the best of the author’s knowledge, this is the first study on the levels of U-II in obese children and adolescents, including a possible link to MS.

Association of resistin (rs3745367) and urotensin II (rs228648 and rs2890565) gene polymorphisms with risk of type 2 diabetes mellitus in Indian population

Insulin resistance may become the most powerful predictor of future development of type 2 diabetes mellitus (T2DM) and a therapeutic target for the treatment of the same. Both Resistin, an adipose derived peptide hormone and Urotensin II a potent vasoconstrictor, are reported to be involved in the development of insulin resistance and T2DM but the results remain contradictory. Therefore, investigations were carried out to study the association of T2DM and single nucleotide polymorphism (SNP) in Resistin (RETN) gene at rs3745367 (+ 299 G > A) and Urotensin II (UTS2) gene at rs228648 (+ 143 G > A) and rs2890565 (+ 3836 C > T) in a North Indian population. Method: The present case-control study, conducted from August 2017 to July 2020, involved 168 T2DM patients and 102 healthy controls. SNPs rs3745367, rs228648 and rs2890565 were amplified from genomic DNA in the studied samples by polymerase chain reaction (PCR) using specific primers. The amplified products were genotyped by restriction fragment length polymorphism (RFLP) using particular restriction endonucleases. Clinical parameters viz. glycosylated haemoglobin (HbA1c), fasting blood glucose (FBG), high density lipoprotein cholesterol (HDL-C), triglycerides (TG), total cholesterol (CHL) and fasting insulin were determined by enzymatic methods. Result and conclusion: A statistically significant association between T2DM and RETN gene at SNP rs3745367 (p = 0.001) and UTS2 gene at SNP rs2890565 (p = 0.001) was observed. In RETN gene SNP rs3745367, insulin and homeostasis model assessment of insulin resistance (HOMA-IR) were found to be higher in GA + AA combined genotype than in GG genotype for T2DM subjects. Regression analysis revealed that SNP rs2890565 and HOMA-IR were independently associated with the risk of development of T2DM when three SNPs were taken as independent variable adjusted for clinical variables. Among four haplotypes, A/T was found associated with increased risk of T2DM as determined for rs228648 and rs2890565 of UTS2 gene. It can be concluded from these results that polymorphism at rs3745367 of RETN gene and at rs2890565 of UTS2 gene are associated with risk of T2DM in North Indian population.

The relationship between urotensin II and insulin resistance in women with gestational diabetes mellitus

AIM

Urotensin II (UII), a pluripotent vasoactive peptide, plays a crucial role in development of insulin resistance. Gestational diabetes mellitus (GDM) is a metabolic disorder associated with insulin resistance. The aims of the current study were to compare UII levels in women with or without GDM and to investigate the relationship between UII and insulin resistance in women with GDM.

METHODS

A total of 84 women were recruited in this case-control study (42 women with GDM and 42 age- and body mass index (BMI)-matched pregnant women without GDM as controls). GDM was diagnosed by a 2-h 75-g oral glucose tolerance test over a period of 24-28 gestational weeks. Circulating UII levels were assessed via the ELISA method. The metabolic parameters of the recruited women were also determined.

RESULTS

The circulating levels of UII in women with GDM were higher than in controls (11.56 ± 4.13 vs. 7.62 ± 3.45 ng/ml, P < 0.001). UII showed a positive correlation with insulin resistance marker (HOMA-IR), fasting blood glucose, and BMI. Moreover, according to the results of multiple linear regression analyses, UII was independently related to HOMA-IR. Additionally, the binary logistic analysis revealed that the women with the highest tertile of UII levels showed increased risk for GDM by comparison with those women with the lowest tertile of UII levels.

CONCLUSION

Elevated UII levels are associated with insulin resistance in women with GDM.

Urotensin-II gene rs228648 polymorphism associated with the risk of diabetes mellitus

Background: Urotensin-II (UII) rs228648 polymorphism has been reported to be associated with the risk of diabetes mellitus (DM) with inconsistent results. The present study sought to reassess the relationship between this polymorphism and susceptibility to DM by meta-analysis.

Methods: Relevant eligible studies and whole genome association study (GWAS) data electronically searched were pooled to evaluate the strength of the association with odds ratios (ORs) and 95% confidence intervals (CIs).

Results: Seven case–control studies involving 894 cases and 1186 controls were finally included in the meta-analysis. Overall analyses indicated that UII gene rs228648 variant was significantly associated with reduced risk of DM (allele, A vs. G: OR = 0.68, 95%CI = 0.56–0.82; dominant, AA+GA vs. GG: OR = 0.70, 95%CI = 0.53–0.91; homozygote, AA vs. GG: OR = 0.41, 95%CI = 0.28–0.61; recessive, AA vs. GA+GG: OR = 0.36, 95%CI = 0.19–0.71). In subgroup analyses based on ethnicity, the results showed a significant association of rs228648 polymorphism with decreased risk of DM in Chinese population under all five genetic models as well as in non-Chinese population under heterozygote and recessive models. Stratified analyses by specific type of DM also presented a significant association for common diabetes mellitus (CDM) under allele and homozygote as well as gestational diabetes mellitus (GDM) under all genetic models except for homozygote model. However, the synthetic analysis with GWAS data suggested an increased risk of DM with rs228648 effect allele in European population (OR = 1.01, 95%CI = 1.00–1.02).

Conclusion: The present meta-analysis preliminarily suggested a potentially opposite role of rs228648 polymorphism associated with DM risk in the Chinese and European population. Further studies are in great request to verify the results.

Plasma urotensin-2 level and Thr21Met but not Ser89Asn polymorphisms of the urotensin-2 gene are associated with migraines

Background

Urotensin-II (U-II) is a peptide recognized by its potent vasoconstrictor activity in many vascular events, however the role of urotensin-II in migraine has not been considered yet. The molecular mechanisms and genetics of migraine have not been fully clarified yet, but it is well-known that vascular changes considerably contribute in pathophysiology of migraine and also its complications. The aim of this study was to analyze the plasma U-II levels along with genotype distributions and allele frequencies for UTS2 Thr21Met and Ser89Asn polymorphisms among the patients with migraine without aura (MWoA).

Methods

One hundred eighty-six patients with MWoA and 171 healthy individuals were included in this study. Plasma U-II levels were measured in attack free period. The genotype and allele frequencies for the Thr21Met (T21M) and Ser89Asn (S89N) polymorphisms in the UTS2 gene were analyzed.

Results

Plasma U-II levels were significantly higher in MWoA patients (p = 0.002). We detected a significant association between the T21M polymorphism in the UTS2 gene and migraine (53.8 % in patients, 40.4 % in controls, p = 0.035), but not with S89N polymorphism (p = 0.620). A significant relationship was found between U-II levels and MIDAS score (β = 0.508, p = 0.001).

Conclusion

Our study suggests that U-II may play a role in migraine pathogenesis; also Thr21Met polymorphism was associated with the risk of migraine disease. Further studies are needed for considering the role of U-II in migraine pathophysiology and for deciding if UTS2 gene may be a novel candidate gene in migraine cases.

International Union of Basic and Clinical Pharmacology. XCII. Urotensin II, urotensin II-related peptide, and their receptor: from structure to function

Urotensin II (UII) is a cyclic neuropeptide that was first isolated from the urophysis of teleost fish on the basis of its ability to contract the hindgut. Subsequently, UII was characterized in tetrapods including humans. Phylogenetic studies and synteny analysis indicate that UII and its paralogous peptide urotensin II-related peptide (URP) belong to the somatostatin/cortistatin superfamily. In mammals, the UII and URP genes are primarily expressed in cholinergic neurons of the brainstem and spinal cord. UII and URP mRNAs are also present in various organs notably in the cardiovascular, renal, and endocrine systems. UII and URP activate a common G protein-coupled receptor, called UT, that exhibits relatively high sequence identity with somatostatin, opioid, and galanin receptors. The UT gene is widely expressed in the central nervous system (CNS) and in peripheral tissues including the retina, heart, vascular bed, lung, kidney, adrenal medulla, and skeletal muscle. Structure-activity relationship studies and NMR conformational analysis have led to the rational design of a number of peptidic and nonpeptidic UT agonists and antagonists. Consistent with the wide distribution of UT, UII has now been shown to exert a large array of biologic activities, in particular in the CNS, the cardiovascular system, and the kidney. Here, we review the current knowledge concerning the pleiotropic actions of UII and discusses the possible use of antagonists for future therapeutic applications.

The relationship of urotensin II with insulin resistance and hs-CRP in patients having PCOS

UrotensinII (UII), one of the most potent vasoconstrictor proteins, may be associated with insulin resistance. The objective of our research was to determine the level of UII in sera of patients with PCOS and to investigate the relationship between UII and insulin resistance in patients with PCOS. Fourty seven PCOS patients and 42 healthy women were included in the study. Serum fasting glucose, insulin, UII, free testosterone and hs-CRP levels of the patients were examined. The HOMA-IR formula was used to calculate insulin resistance. Insulin sensitivity was calculated by using the QUICKI-IS formula. The two groups did not show any a significant difference in terms of age and BMI (p > 0.05). Serum UII, hs-CRP, insulin levels and the HOMA-IR were significantly higher in the patients with PCOS (p < 0.05). In the analysis of the correlation, UII and HOMA-IR showed statistically significant, moderately strong and positive correlation(r = 044, p < 0.001). UII and QUICKI-IS showed statistically significant, moderately strong and negative correlation(r = -0.44, p < 0.001). Also, a significant and positive correlation was found between with UII and hs-CRP(r = 0.51, p < 0.001). Our study data suggested that UII may have a role in the pathophysiology of insulin resistance and increased cardiovascular risk, which are commonly found in patients with PCOS.

Urotensin-II Ligands: An Overview from Peptide to Nonpeptide Structures

Urotensin-II was originally isolated from the goby urophysis in the 1960s as a vasoactive peptide with a prominent role in cardiovascular homeostasis. The identification of human isoform of urotensin-II and its specific UT receptor by Ames et al. in 1999 led to investigating the putative role of the interaction U-II/UT receptor in multiple pathophysiological effects in humans. Since urotensin-II is widely expressed in several peripheral tissues including cardiovascular system, the design and development of novel urotensin-II analogues can improve knowledge about structure-activity relationships (SAR). In particular, since the modulation of the U-II system offers a great potential for therapeutic strategies related to the treatment of several diseases, like cardiovascular diseases, the research of selective and potent ligands at UT receptor is more fascinating. In this paper, we review the developments of peptide and nonpeptide U-II structures so far developed in order to contribute also to a more rational and detectable design and synthesis of new molecules with high affinity at the UT receptor.

A closer look at the role of urotensin II in the metabolic syndrome

Urotensin II (UII) is a vasoactive peptide that was first discovered in the teleost fish, and later in mammals and humans. UII binds to the G protein coupled receptor GPR14 (now known as UT). UII mediates important physiological and pathological actions by interacting with its receptor. The metabolic syndrome (MetS) is described as cluster of factors such as obesity, dyslipidemia, hypertension, and insulin resistance (IR), further leading to development of type 2 diabetes mellitus and cardiovascular diseases. UII levels are upregulated in patients with the MetS. Evidence directly implicating UII in every risk factor of the MetS has been accumulated. The mechanism that links the different aspects of the MetS relies primarily on IR and inflammation. By directly modulating both of these factors, UII is thought to play a central role in the pathogenesis of the MetS. Moreover, UII also plays an important role in hypertension and hyperlipidemia thereby contributing to cardiovascular complications associated with the MetS.

Association Between Thr21Met and Ser89Asn Polymorphisms of the Urotensin II Gene and Systemic Sclerosis

Objective.

Systemic sclerosis (SSc) is an autoimmune chronic fibrotic disorder. Urotensin II (U-II) is predominantly a vasoactive peptide with fibrotic and prothrombotic features. Like endothelin-1 (ET-1), U-II could play an important role in SSc pathogenesis. We evaluated the possible role of the U-II gene polymorphisms (Thr21Met and Ser89Asn) in the genetic susceptibility to SSc in a Turkish population.

Methods.

A total of 189 patients with SSc and 205 healthy controls were enrolled in our study. We analyzed the genotype and allele frequencies of the U-II (UTS2) gene polymorphisms Thr21Met and Ser89Asn in patients with SSc and in controls.

Results.

We found that the Thr21Met polymorphism of the UTS2 gene was markedly associated with the risk of developing SSc (p < 0.0001), but there was no relationship between the Ser89Asn polymorphism and SSc (p > 0.05). Two haplotypes (MS and TS) were markedly associated with SSc (p < 0.05). There were significant associations between the genotype and allele frequencies of UTS2 gene Thr21Met polymorphism and cases with diffuse or limited SSc, systemic or lung involvement, finger flexion deformity, pitting scars at the fingertips, positive anticentromere, or positive antitopoisomerase 1 antibody groups.

Conclusion.

Our study shows the association between Thr21Met, but not Ser89Asn, in the UTS2 gene and SSc. The results strongly suggest that this single-nucleotide polymorphism may be an important risk factor in the development of SSc, and a powerful indicator of severe skin and lung involvement in patients with SSc.

Potential Clinical Implications of the Urotensin II Receptor Antagonists

Urotensin II (UII) binds to its receptor, UT, playing an important role in the heart, kidneys, pancreas, adrenal gland, and central nervous system. In the vasculature, it acts as a potent endothelium-independent vasoconstrictor and endothelium-dependent vasodilator. In disease states, however, this constriction–dilation equilibrium is disrupted. There is an upregulation of the UII system in heart disease, metabolic syndrome, and kidney failure. The increase in UII release and UT expression suggest that UII system may be implicated in the pathology and pathogenesis of these diseases by causing an increase in acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT-1) activity leading to smooth muscle cell proliferation and foam cell infiltration, insulin resistance (DMII), as well as inflammation, high blood pressure, and plaque formation. Recently, UT antagonists such as SB-611812, palosuran, and most recently a piperazino-isoindolinone based antagonist have been developed in the hope of better understanding the UII system and treating its associated diseases.

Urotensin-II 143 G/A polymorphism is not associated with the risk of preeclampsia in Korean women

PROBLEM

Urotensin-II (UTS-II) may be associated with preeclampsia. We therefore assessed whether the UTS-II 143 G/A polymorphism is associated with preeclampsia in Korean women.

METHOD OF STUDY

This prospective case-control study enrolled 109 patients with preeclampsia and 144 healthy pregnant controls, all of whom were genotyped for the UTS-II 143 G/A polymorphism using the real-time TaqMan SNP Genotyping Assay.

RESULTS

There was no significant difference in the distribution of the 143 G/A polymorphism or the frequency of the 143 A allele between women with preeclampsia and controls. In a dominant model, carriers of the A allele were not significantly more prevalent in the preeclamptic (53.2%) than in the control (60.4%) group. In addition, subgroup analysis showed no significant difference in genotype distribution or allelic frequency of the 143 G/A polymorphism between women with mild or severe preeclampsia and controls.

CONCLUSION

In Korean women, the common UTS-II 143 G/A polymorphism is unlikely to have an association with the risk of preeclampsia.

Association analysis of urotensin II gene (UTS2) and flanking regions with biochemical parameters related to insulin resistance

Background

Urotensin II (UII) is a potent vasoconstrictor peptide, which signals through a G-protein coupled receptor (GPCR) known as GPR14 or urotensin receptor (UTR). UII exerts a broad spectrum of actions in several systems such as vascular cell, heart muscle or pancreas, where it inhibits insulin release.

Objective

Given the reported role of UII in insulin secretion, we have performed a genetic association analysis of the UTS2 gene and flanking regions with biochemical parameters related to insulin resistance (fasting glucose, glucose 2 hours after a glucose overload, fasting insulin and insulin resistance estimated as HOMA).

Results and Conclusions

We have identified several polymorphisms associated with the analysed clinical traits, not only at the UTS2 gene, but also in thePER3 gene, located upstream from UTS2. Our results are compatible with a role for UII in glucose homeostasis and diabetes although we cannot rule out the possibility that PER3 gene may underlie the reported associations.

Raised plasma urotensin II in type 2 diabetes patients is associated with the metabolic syndrome phenotype

Urotensin II (UII) exerts multiple effects on the cardiovascular system, acts as a diabetogenic agent, and may also contribute to the development of the metabolic syndrome (MetS). The aim of this study was to determine circulating UII in patients with type 2 diabetes mellitus (T2DM) and its relationship with MetS. A total of 360 consecutive patients with T2DM were included. MetS presence/absence (MetS [+]/[-]) was defined according to American Heart Association/National Heart, Lung and Blood Institute criteria. Plasma concentrations of UII were determined by radioimmunoassay. UII levels were significantly higher in MetS (+) than in MetS (-) T2DM patients (0.97 pg/mL [0.93-1.01], n=294 vs 0.82 pg/mL [0.75-0.88] pg/mL, n=66, respectively; P<.001). Multiple logistic regression analysis showed that UII was significantly associated with MetS (+) (odds ratio, 6.41 [95% confidence interval, 1.21-16.04]; P=.02). UII plasma concentrations are significantly higher in T2DM patients presenting with MetS. Therefore, circulating UII may participate in the worsening course of some T2DM patients and may provide novel therapeutic perspectives.

Elevated expression of urotensin II and its receptor in great artery of type 2 diabetes and its significance

Urotensin II (U-II) and its receptor G-protein-coupled receptor GPR14 (UT) exert a broad spectrum of biological functions such as vascular remodeling and vasoactive cardiac inotropic. Now some preclinical and clinical studies showing that they may play an important role in insulin resistance. Then to research the role of U-II and UT in the vascular complication of type 2 diabetes especially in the big artery, we chose the GK rat who is the diabete-2 naturally. Through the HE stain and red oil O stain to chose the artery specimens that have no Atheromatous plaque, no Fatty streak and no Fibrous plaque. The immunohistochemistry and reverse transcription polymerase chain reaction (RT-PCR) to determine the degree of the expression and location of U-II and UT in the aorta. We found that U-II was significant up-regulated in the endothelial cell and adventitia of GK rat compared with healthy controls on both protein and mRNA levels. The UT was only highly enhanced in the endothelial. In the adventitia there is no difference on the quantity between two of them, These results suggest that the U-II and UT play an important role in the diabetic angiopathy especially in the large artery and maybe imply a new way to prevent the injury of artery in the diabete-2 patient.

Effect of the urotensin-II receptor antagonist palosuran on secretion of and sensitivity to insulin in patients with Type 2 diabetes mellitus

AIMS

To investigate the effects of palosuran, a nonpeptidic, potent and selective antagonist of the urotensin-II receptor, on insulin and glucose regulation in 20 diet-treated patients with Type 2 diabetes mellitus in a double-blind, placebo-controlled, randomized, crossover, proof-of-concept study.

METHODS

After 4 weeks' oral treatment with 125 mg palosuran or placebo b.i.d.,effects on insulin secretion and sensitivity and blood glucose levels were assessed by means of a hyperglycaemic glucose clamp, meal tolerance test, homeostasis model assessment-insulin resistance score, and daily self-monitoring of blood glucose. Plasma concentrations of palosuran were determined for 12 h on the last day of intake.

RESULTS

Palosuran did not affect second-phase insulin response (primary end-point) during the hyperglycaemic glucose clamp in comparison with placebo [paired difference of -1.8 microU ml(-1), 95% confidence interval (CI) -7.8, 4.2]. Likewise, no effects of palosuran were detected on the first-phase insulin response, or on insulin secretion and blood glucose levels during the meal tolerance test or on homeostasis model assessment-insulin resistance score. No clinically significant effects on daily blood glucose profiles were observed during the study. Geometric mean C(max) and AUC(tau) (95% CI) and median t(max) (range) in this patient population were 180 ng ml(-1) (125, 260), 581 ng.h ml(-1) (422, 800) and 3.0 h (0.67, 4.3), respectively.

CONCLUSIONS

The results of this study indicate that antagonism of the urotensin-II system does not influence insulin secretion or sensitivity or daily blood glucose levels in diet-treated patients with Type 2 diabetes.

Increased plasma urotensin-II levels are associated with diabetic retinopathy and carotid atherosclerosis in Type 2 diabetes

Human U-II (urotensin-II), the most potent vasoconstrictor peptide identified to date, is associated with cardiovascular disease. A single nucleotide polymorphism (S89N) in the gene encoding U-II (UTS2) is associated with the onset of Type 2 diabetes and insulin resistance in the Japanese population. In the present study, we have demonstrated a relationship between plasma U-II levels and the progression of diabetic retinopathy and vascular complications in patients with Type 2 diabetes. Eye fundus, IMT (intima-media thickness) and plaque score in the carotid artery, BP (blood pressure), FPG (fasting plasma glucose), HbA(1c) (glycated haemoglobin), U-II, angiogenesis-stimulating factors, such as VEGF (vascular endothelial growth factor) and heregulin-beta(1), and lipid profiles were determined in 64 patients with Type 2 diabetes and 24 non-diabetic controls. FPG, HbA(1c) and VEGF levels were significantly higher in patients with Type 2 diabetes than in non-diabetic controls. Diabetes duration, insufficient glycaemic and BP control, plasma U-II levels, IMT, plaque score and nephropathy grade increased significantly across the subjects as follows: non-diabetic controls, patients with Type 2 diabetes without retinopathy (group N), patients with Type 2 diabetes with simple (background) retinopathy (group A) and patients with Type 2 diabetes with pre-proliferative and proliferative retinopathy (group B). The prevalence of obesity and smoking, age, low-density lipoprotein, triacylglycerols (triglycerides) and heregulin-beta(1) were not significantly different among the four groups. In all subjects, U-II levels were significantly positively correlated with IMT, FPG, and systolic and diastolic BP. Multiple logistic regression analysis revealed that, of the above parameters, U-II levels alone had a significantly independent association with diabetic retinopathy. In conclusion, the results of the present study provide the first evidence that increased plasma U-II levels may be associated with the progression of diabetic retinopathy and carotid atherosclerosis in patients with Type 2 diabetes.

Uric acid stimulates endothelin-1 gene expression associated with NADPH oxidase in human aortic smooth muscle cells

AIM

Recent experimental and human studies have shown that hyperuricemia is associated with hypertension and cardiovascular diseases. Elevated levels of endothelin-1 (ET-1) has been regarded as one of the most powerful independent predictors of cardiovascular diseases. For investigating whether uric acidinduced vascular diseases are related to ET-1, the uric acid-induced ET-1 expression in human aortic smooth muscle cells (HASMC) was examined.

METHODS

Cultured HASMC treated with uric acid, cell proliferation and ET-1 expression were examined. Antioxidant pretreatments on uric acid-induced extracellular signal-regulated kinases (ERK) phosphorylation were carried out to elucidate the redox-sensitive pathway in proliferation and ET-1 gene expression.

RESULTS

Uric acid was found to increase HASMC proliferation, ET-1 expression and reactive oxygen species production. The ability of both N-acetylcysteine and apocynin (1-[4-hydroxy-3-methoxyphenyl]ethanone, a NADPH oxidase inhibitor) to inhibit uric acid-induced ET-1 secretion and cell proliferation suggested the involvement of intracellular redox pathways. Furthermore, apocynin, and p47phox small interfering RNA knockdown inhibited ET-1 secretion and cell proliferation induced by uric acid. Inhibition of ERK by U0126 (1,4-diamino-2,3-dicyano- 1,4-bis[2-aminophenylthio]butadiene) significantly suppressed uric acid-induced ET-1 expression, implicating this pathway in the response to uric acid. In addition, uric acid increased the transcription factor activator protein-1 (AP-1) mediated reporter activity, as well as the ERK phosphorylation. Mutational analysis of the ET-1 gene promoter showed that the AP-1 binding site was an important cis-element in uric acid-induced ET-1 gene expression.

CONCLUSION

This is the first observation of ET-1 regulation by uric acid in HASMC, which implicates the important role of uric acid in the vascular changes associated with hypertension and vascular diseases.

Structure-activity relationships of urotensin II and URP

Urotensin II (U-II) and urotensin II-related peptide (URP) are the endogenous ligands for the orphan G-protein-coupled receptor GPR14 now renamed UT. At the periphery, U-II and/or URP exert a wide range of biological effects on cardiovascular tissues, airway smooth muscles, kidney and endocrine glands, while central administration of U-II elicits various behavioral and cardiovascular responses. There is also evidence that U-II and/or URP may be involved in a number of pathological conditions including heart failure, atherosclerosis, renal dysfunction and diabetes. Because of the potential involvement of the urotensinergic system in various physiopathological processes, there is need for the rational design of potent and selective ligands for the UT receptor. Structure-activity relationship studies have shown that the minimal sequence required to retain full biological activity is the conserved U-II(4-11) domain, in particular the Cys5 and Cys10 residues involved in the disulfide bridge, and the Phe6, Lys8 and Tyr9 residues. Free alpha-amino group and C-terminal COOH group are not necessary for the biological activity, and modifications of these radicals may even increase the stability of the analogs. Punctual substitution of native amino acids, notably Phe6 and Trp7, by particular residues generates analogs with antagonistic properties. These studies, which provide crucial information regarding the structural and conformational requirements for ligand-receptor interactions, will be of considerable importance for the design of novel UT ligands with increased selectivity, potency and stability, that may eventually lead to the development of innovative drugs.

Urotensin-II and cardiovascular remodeling

Urotensin-II (U-II), a cyclic undecapeptide, and its receptor, UT, have been linked to vascular and cardiac remodeling. In patients with coronary artery disease (CAD), it has been shown that U-II plasma levels are significantly greater than in normal patients and the severity of the disease is increased proportionally to the U-II plasma levels. We showed that U-II protein and mRNA levels were significantly elevated in the arteries of patients with coronary atherosclerosis in comparison to healthy arteries. We observed U-II expression in endothelial cells, foam cells, and myointimal and medial vSMCs of atherosclerotic human coronary arteries. Recent studies have demonstrated that U-II acts in synergy with mildly oxidized LDL inducing vascular smooth muscle cell (vSMC) proliferation. Additionally, U-II has been shown to induce cardiac fibrosis and cardiomyocyte hypertrophy leading to cardiac remodeling. When using a selective U-II antagonist, SB-611812, we demonstrated a decrease in cardiac dysfunction including a reduction in cardiomyocyte hypertrophy and cardiac fibrosis. These findings suggest that U-II is undoubtedly a potential therapeutic target in treating cardiovascular remodeling.

Cardiorenovascular effects of urotensin II and the relevance of the UT receptor

Urotensin II (U-II) is a vasoactive peptide with many potent effects in the cardiorenovascular system. U-II activates a G-protein-coupled receptor termed UT. UT and U-II are highly expressed in the cardiovascular and renal system. Patients with various cardiovascular diseases show high U-II plasma levels. It was demonstrated that elevated U-II plasma levels and increased UT expression seem to play a role in heart failure, end-stage renal disease and atherosclerosis. U-II induces potent changes in vascular tone regulation. In addition, U-II stimulates vascular smooth muscle cell proliferation and cardiomyocyte hypertrophy. Currently several pharmaceutical companies are developing compounds to control the U-II/UT system. There are preclinical and some clinical studies showing potential benefits of inhibiting U-II function in renal disease, heart failure, and diabetes. This article will review both pre- and clinical data concerning cardiorenovascular effects of U-II.

The role of urotensin II in the metabolic syndrome

Urotensin II is a potent vasoconstrictive peptide that mediates both endothelium-independent vasoconstriction and endothelium-dependent vasodilatation. Its plasma level correlates positively with body weight and is raised in diabetes, renal failure, hypertension, and other cardiovascular diseases including congestive heart failure and carotid atherosclerosis. It can inhibit glucose-induced insulin secretion, and genetic variants in urotensin II gene are associated with insulin resistance and type 2 diabetes. Urotensin II also affects lipid metabolism in fish and food intake in mice. Recent studies have also demonstrated a role of urotensin II in inflammation and endothelial dysfunction. These findings suggest a close relationship between urotensin II and at least some components of the metabolic syndrome, including hypertension, insulin resistance, hyperglycemia, and inflammation.

Role of urotensin II and its receptor in health and disease

Urotensin II (U-II) is currently the most potent vasoconstrictor identified. This action is brought about via activation of a G(q/11)-protein coupled receptor (UT receptor). U-II activation of the UT receptor increases inositol phosphate turnover and intracellular Ca(2+). In addition to producing vasoconstriction, dilation and ionotropic effects have also been described. There is considerable variation in the responsiveness of particular vascular beds from the same and different species, including humans. Receptors for U-II are located peripherally on vascular smooth muscle (contractile responses) and endothelial cells (dilatory responses via nitric oxide). In humans, plasma U-II is elevated in heart failure, renal failure, liver disease, and diabetes. Iontophoresis of U-II in healthy volunteers produces vasodilation (of the forearm) while in patients with heart failure or hypertension a constriction is observed. To date there is only one clinical study using a UT receptor antagonist (palosuran) in diabetic patients with macroalbuminuria. This antagonist reduced albumin excretion, probably by increasing renal blood flow. Studies in other disease conditions are eagerly awaited. In summary, the U-II / UT receptor system has clinical potential, and for the anesthesiologist, this novel peptide-receptor system may be of use in the intensive care unit.

Hemodynamic effects of chronic urotensin II administration in animals with and without aorto-caval fistula

Urotensin II (UTII) is a potent vasoactive peptide. Recent studies have demonstrated increased expression of both UTII and its receptor (UTR) expression in end-stage congestive heart failure (CHF), but it is unclear whether UTII and UTR are late stage markers of decompensation, or earlier adaptive responses. The purpose of this study was to measure the effects of chronic UTII administration in normal and volume overloaded animals. Chronic 4 weeks administration of UTII produced decreases in hemodynamic function in animals not subjected to volume overload while returning function to control levels in animals with overload. Expression levels of calcium regulatory proteins phospholamban (PLN), sarcoplasmic reticulum Ca(2+) ATPase (SERCA2), and Na(+)/Ca(2+) exchanger (NCX) were measured to determine if administration of UTII resulted in aberrant Ca(2+) handling. Changes in protein expression revealed that UTII influenced Ca(2+) handling proteins in normal animals although these changes are not seen in the volume overload.

Human urotensin II as a link between hypertension and coronary artery disease

Hypertension is a well-known risk factor for atherosclerosis, but the molecular mechanisms that link elevated blood pressure to the progression of atherosclerosis remain unclear. Human urotensin II (U-II), the most potent endogenous vasoconstrictor peptide identified to date, and its receptor (UT receptor) are involved in the etiology of essential hypertension. In patients with essential hypertension, U-II infused into the forearm brachial artery has been shown to induce vasoconstriction. Recent studies have demonstrated elevated plasma U-II concentrations in patients with essential hypertension, diabetes mellitus, atherosclerosis, and coronary artery disease. U-II is expressed in endothelial cells, macrophages, macrophage-derived foam cells, and myointimal and medial vascular smooth muscle cells (VSMCs) of atherosclerotic human coronary arteries. UT receptors are present in VSMCs of human coronary arteries, the thoracic aorta and cardiac myocytes. Lymphocytes are the most active producers of U-II, whereas monocytes and macrophages are the major cell types expressing UT receptors, with relatively little receptor expression in foam cells, lymphocytes, and platelets. U-II accelerates foam cell formation by up-regulation of acyl-coenzyme A:cholesterol acyltransferase-1 in human monocyte-derived macrophages. In human endothelial cells, U-II promotes cell proliferation and up-regulates type 1 collagen expression. U-II also activates nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and plasminogen activator inhibitor-1 in human VSMCs, and stimulates VSMC proliferation with synergistic effects observed when combined with oxidized low-density lipoprotein, lysophosphatidylcholine, reactive oxygen species or serotonin. These findings suggest that U-II plays key roles in accelerating the development of atherosclerosis, thereby leading to coronary artery disease.

Haplotypes in the urotensin II gene and urotensin II receptor gene are associated with insulin resistance and impaired glucose tolerance

We studied single nucleotide polymorphisms (SNPs) and haplotypes in the urotensin-II (UTS2) and urotensin-II receptor gene (UTS2R) in Hong Kong Chinese (224 hypertensive and 306 normotensive unrelated subjects) and their relation to hypertension and the metabolic syndrome. For UTS2, the GGT haplotype (-605G, 143G and 3836T) was associated with higher plasma level of U-II and insulin, and higher homeostasis model assessment of insulin resistance index and beta-cell function. For UTS2R, the AC haplotype (-11640A and -8515C) was associated with higher 2 h plasma glucose after a 75 g oral glucose load. Therefore, U-II and its receptor may play a role in insulin resistance.

Urotensin II: its function in health and its role in disease

Urotensin II (U-II) is the most potent vasoconstrictor known, even more potent than endothelin-1. It was first isolated from the fish spinal cord and has been recognized as a hormone in the neurosecretory system of teleost fish for over 30 years. After the identification of U-II in humans and the orphan human G-protein-coupled receptor 14 as the urotensin II receptor, UT, many studies have shown that U-II may play an important role in cardiovascular regulation. Human urotensin II (hU-II) is an 11 amino acid cyclic peptide, generated by proteolytic cleavage from a precursor prohormone. It is expressed in the central nervous system as well as other tissues, such as kidney, spleen, small intestine, thymus, prostate, pituitary, and adrenal gland and circulates in human plasma. The plasma U-II level is elevated in renal failure, congestive heart failure, diabetes mellitus, systemic hypertension and portal hypertension caused by liver cirrhosis. The effect of U-II on the vascular system is variable, depending on species, vascular bed and calibre of the vessel. The net effect on vascular tone is a balance between endothelium-independent vasoconstriction and endothelium-dependent vasodilatation. U-II is also a neuropeptide and may play a role in tumour development. The development of UT receptor antagonists may provide a useful research tool as well as a novel treatment for cardiorenal diseases.

Magnifying endoscopic observation of the gastric mucosa, particularly in patients with atrophic gastritis

The gastric mucosal surface was observed using the magnifying fibergastroscope (FGS-ML), and the fine gastric mucosal patterns, which were even smaller than one unit of gastric area, were examined at a magnification of about 30. For simplicification, we classified these patterns by magnifying endoscopy in the following ways; FP, FIP, FSP, SP and MP, modifying Yoshii's classification under the dissecting microscope. The FIP, which was found to have round and long elliptical gastric pits, is a new addition to our endoscopic classification. The relationship between the FIP and the intermediate zone was evaluated by superficial and histological studies of surgical and biopsy specimens. The width of the band of FIP seems to be related to the severity of atrophic gastritis. Also, the transformation of FP to FIP was assessed by comparing specimens taken from the resected and residual parts of the stomach, respectively. Moreover, it appears that severe gastritis occurs in the gastric mucosa which shows a FIP. Therefore, we consider that the FIP indicates the position of the atrophic border.